The flowers are in shade, which makes the interior of the flower more difficult to see. Maybe some fill flash would have opened up the shadows some. The shallow depth of field is good but it could stand to be a little softer.
Also, try photographing the flowers from an angle rather than dead on. This will make the composition more interesting. Also, try not to center the flowers in the frame, because that also makes the image less interesting. You could also concentrate on just one or two rather than the whole bunch of them
I changed the crop a little so they were not in the dead center, lightened the flowers somewhat and blurred the background a little more in PS but they are still kind of void of much detail.